"I taught all three of the sisters, at one time or another," Simone said. "Jessica seemed quite competent when she was younger, and she worked hard, but as she grew she became cripplingly self-conscious, to the point where any individual exercises seemed to be a painful ordeal for her. I told her parents I thought it would be better if she didn't have to go through this any more."

"And Rosalind?" Cassie asked.

"Rosalind had some talent, but she lacked application and wanted instant results. After a few months she switched to, I believe, violin lessons. She said it was by her parents' choice, but I thought it was because she was bored. We see this quite often with young children: when they aren't immediately proficient, and when they realize how much hard work is involved, they become frustrated and leave. Frankly, neither of them would ever have been Royal Ballet School material in any case."

"But Katy…" Cassie said, leaning forward.

Simone looked at her for a long time. "Katy was…sérieuse."

That was what gave her voice some of its distinctive quality: somewhere, far back, there was a touch of French shaping the intonations. "Serious," I said.

"More than that," said Cassie. Her mother was half French, and as a child she spent summers with her grandparents in Provence; she says she's forgotten most of her spoken French at this point, but she still understands it. "A professional."

Simone inclined her head. "Yes. She loved even the hard work-not only for the results it brought, but for its own sake. A real talent for dance is not common; the temperament to make a career of it is much rarer. To find both at once…" She looked away again. "Sometimes, on evenings when only one studio was being used, she would ask if she could come in and practice in the other."

Outside, the light was beginning to dim towards evening; the skateboard kids' calls floated up, faint and crystalline through the glass. I thought of Katy Devlin alone in the studio, watching the mirror with detached absorption as she moved in slow spins and dips; the lift of a pointed foot; streetlamps throwing saffron rectangles across the floor, Satie's Gnossiennes on the crackly record player. Simone seemed pretty sérieuse herself, and I wondered how on earth she had ended up here: above a shop in Stillorgan, with the smell of grease wafting up from the chip shop next door, teaching ballet to little girls whose mothers thought it would give them good posture or wanted framed pictures of them in tutus. I realized, suddenly, what Katy Devlin must have meant to her.

"How did Mr. and Mrs. Devlin feel about Katy going to ballet school?" Cassie asked.

"They were very supportive," Simone said, without hesitation. "I was relieved, and also surprised; not every parent is willing to send a child that age away to school, and most, with good reason, are opposed to their children becoming professional dancers. Mr. Devlin, in particular, was very much in favor of Katy going. He was close to her, I think. I admired this, that he wanted what was best for her even if it meant letting her go away."

"And her mother?" Cassie said. "Was she close to her?"

Simone gave a little one-shouldered shrug. "Less, I think. Mrs. Devlin is…rather vague. She always seemed bewildered by all of her daughters. I think perhaps she isn't very intelligent."

"Have you noticed anyone strange hanging around in the past few months?" I asked. "Anyone who worried you?" Ballet schools and swimming clubs and scout troops are pedophile magnets. If someone had been looking for a victim, this was the obvious place where he might have spotted Katy.

"I understand what you mean, but no. We look for this. About ten years ago a man used to sit on a wall up the hill and look into the studio through binoculars. We complained to the police, but they did nothing until he tried to convince one little girl to get into his car. Since then we're very watchful."

"Did anyone take an interest in Katy to a level that you felt was unusual?"

She thought, shook her head. "No one. Everyone admired her dancing, many people supported the fund-raiser we held to help with her fees, but no one person more than others."

"Was there any jealousy of her talent?"

Simone laughed, a quick hard breath through her nose. "These are not stage parents we have here. They want their daughters to learn a little ballet, enough to be pretty; they don't want them to make a career of it. I'm sure a few of the other little girls were envious, yes. But enough to kill her? No."

She looked, suddenly, exhausted; her elegant pose hadn't changed, but her eyes were glazed with fatigue. "Thank you for your time," I said. "We'll contact you if we need to ask you any more questions."

"Did she suffer?" Simone asked abruptly. She wasn't looking at us.

She was the first person to ask. I started to give the standard non-answer involving the post-mortem results, but Cassie said, "There's no evidence of that. We can't be sure of anything yet, but it seems to have been quick."

Simone turned her head with an effort and met Cassie's eyes. "Thank you," she said.

She didn't get up to see us out, and I realized it was because she wasn't sure she could do it. As I closed the door I caught a last glimpse of her through the round window, still sitting straight-backed and motionless with her hands folded in her lap: a queen in a fairy tale, left alone in her tower to mourn her lost, witch-stolen princess.

"'I'm not going to get sick any more,'" Cassie said, in the car. "And she stopped getting sick."

"Willpower, like Simone said?"

"Maybe." She didn't sound convinced.

"Or she could have been making herself sick," I said. "Vomiting and diarrhea are both pretty easy to induce. Maybe she was looking for attention, and once she got into ballet school she didn't need to any more. She was getting plenty of attention without being sick-newspaper articles, fund-raisers, the lot… I need a cigarette."

"Junior Munchausen syndrome?" Cassie reached into the back, dug around in my jacket pockets and found my smokes. I smoke Marlboro Reds; Cassie has no particular brand loyalty but generally buys Lucky Strike Lights, which I consider to be girl cigarettes. She lit two and passed one to me. "Can we pull medical records on the two sisters as well?"

"Dodgy," I said. "They're alive, so there's confidentiality. If we got the parents' consent…" She shook her head. "Why, what are you thinking?"

She opened her window a few inches, and the wind blew her hair sideways. "I don't know… The twin, Jessica-the bunny-in-headlights thing could just be stress from Katy being missing, but she's way too thin. Even through that big huge woolly thing you could tell she's half the size of Katy, and Katy was no heifer. And then the other sister…There's something off about her, too."

"Rosalind?" I said.

There must have been something funny in my tone. Cassie shot me an oblique glance. "You liked her."

"Yes, I suppose I did," I said, defensive and not sure why. "She seemed like a nice girl. She's very protective of Jessica. What, you didn't?"

"What's that got to do with it?" Cassie said coolly and, I felt, a little unfairly. "Regardless of who likes her, she dresses funny, she wears too much makeup-"

"She's well groomed, so there's something wrong with her?"

"Please, Ryan, do us both a favor and grow up; you know exactly what I mean. She smiles at inappropriate times, and, as you spotted, she wasn't wearing a bra." I had noticed that, but I hadn't realized that Cassie had as well, and the dig irritated me. "She may well be a very nice girl, but there's something off there."

I didn't say anything. Cassie threw the rest of her cigarette out the window and dug her hands into her pockets, slumped in her seat like a sulky teenager. I turned on dipped headlights and sped up. I was annoyed with her and I knew she was annoyed with me, too, and I wasn't sure quite how this had happened.